Wednesday, September 09, 2015

"Silent mode"

Moon of Alabama made an important catch. As you may have read, the anti-Assad Nusra Front (also known as Al Qaeda in Syria) has battled American-trained mercenaries in Syria -- the guys described as "moderate" and "vetted" by our media. Apparently, there is phone video of Nusra fighters being blasted by "automatic weapons fire." That's the term used by the NYT.

Did that fire come from a drone? Maybe, but that theory has problems...

No drone I am aware of and certainly not the "Predator" are equipped with automatic weapons like machine guns. The Drones carry fire-and-forget missiles or bombs but no drone has the necessarily heavy rotating tower and swiveling weapon holder that would allow the use of automatic weapons. "Automatic fire from the sky" as the reporter describes from the video he has seen can only have come from manned helicopters. Or is there some other explanation that I miss?

If there were helicopters who's birds were these? U.S. or Turkish? Are there more of these flying over Syria and to what purpose? And what would be the Search & Rescue assets that could be used should such a bird come down involuntarily?

Something we are not told about is happening at the Turkish-Syrian border.

Either that, or drones are capable of things that we mere mortals are not supposed to know about.

Silent. The M of A story referenced above evinced one interesting comment:

Although many people have seen that video, few have asked a should-be-obvious question: Why didn't the victims hear the chopper?

I would love to write a long post about the history of silent aircraft. Unfortunately, I can't: The data is kept hidden from scurvy knaves like me and thee.

But I'm reasonably sure of this much: There were striking advances in this field as far back as the 1960s, possibly earlier. (According to Wikipedia, the first patent in active noise control was filed in 1934.)

A long time ago -- circa 1980, when I was a not-terribly-political young doofus -- I was told that a military contractor named Bolt, Baranek and Newman (now BBN Technologies) had developed a technology called "antisound." The basic idea was later commercialized in noise cancelling headphones.

As most of you know, loudspeakers come in enclosures because an unenclosed speaker emits one sound wave in front and the exact opposite wave in back. One wave cancels the other; without the enclosure, the sound is tinny and weak. If you were to amplify the inverse sound wave, you could theoretically cancel out the original noise completely. Theoretically.

This technique works best with noises that are constant or repetitive. But you already knew that, if you own a pair of noise-cancelling headphones.

I have reason to believe that the military has been using antisound to silence aircraft since the 1960s. One obvious application: Disguising aircraft used in the exfiltration of paramilitary operatives behind enemy lines.

Unseen. And that brings us to the topic of invisible aircraft. Dare ye scoff, ye scoffing scoffers? Scoff no more! Also here. Also (and this one is really wild) here.

We are forever being told that invisibility tech is soon-to-come but not-yet-arrived. I believe that it is already operational, and has been for some years.

All of which brings us to today's Big Question: What if some "drone attacks" do not actually involve drones? What if the "drone" was actually a very stealthy helicopter?

The Air Force has flown fixed wing airplane drones for over 50 years, including 'heavies'(large airframes) in military exercises and other scenarios.

I have never heard of drone helicopters, but I think they surely must exist.

XI

posted by Anonymous : 1:23 AM

The automatic weapons fire could be from the ground. Could be from an AC-130.

As for helicopters, there are many ways to make the silent, or at least quieter. Just unevenly spacing the rotor blades will significantly reduce the noise. Also, interposing a mile or two between the chopper and its victim will make it almost impossible to hear.

As for helicopter drones, what's the point? Just use fixed-wing ones. Helicopter drones really have no advantages. Similarly, there's really no reason to use a silenced helicopter than to use a drone.

Another possible reason why the victims in the aforementioned video didn't hear the helicopter that attacked them is probably that the air was thick with helicopters during that time, so an Apache in a hover a few hundred yards away just may not have stood out above the din.

Also, the Apache is a four-bladed helicopter, which significantly reduces the noise factor by allowing the rotor to spin more slowly while still generating more lift than a two-bladed "chopper" could.

As an example, the original Huey helicopters used in Vietnam were two-bladed versions which needed to spin faster to generate the requisite lift. As such, the tips of the blades were actually breaking the sound barrier as they spun, resulting in the familiar thump-thump-thump sound. A four-bladed helicopter is much, much quieter and doesn't require any sci-fi technology to achieve that end.

I was watching the fireworks in Boston this year and a police helicopter pulled into a hover about 200' above the rooftop where we were standing. Even though the downdraft was blowing cups off the table, it was surprisingly quiet.

holy shit, I used to work for BBN in the mid nineties, never heard anything like that. They were strictly telecom as far as I know, They developed the ARPANET later Milnet, old X.25 nodes, especially at that time. They have since sold off that portion ( I believe what is left of that is now called Level 3) I think they mostly develop high level cryptography now... Just was shocked to see that old blast from the past on this page... ;)

Unknown: I might as well tell all. While in college -- and starving, as usual -- I answered an ad looking for paid volunteers for an experiment. I was told to go out to a facility in the SF Valley -- and lo and behold, it was run by BBN. The name was recognizable because they had figured in the then-recent HSCA investigation.

They put me in this acoustically dead-silent room -- lots of padding. They placed heavy super-headphones over my ears and tested my hearing. In the end, they did not use me, I think because my hearing was better than normal. (THEN.)

But while I was waiting in the antechamber, I read a pamphlet which explained BBN's involvement with antisound technology. It was fascinating! I asked someone who worked there about it, and he was surprisingly chatty, even though the technology had hush-hush military applications. ("Hush-hush." Get it?)

Afterwards, I told my friends that there was a new way to make helicopters and other machines artificially silent. They didn't believe me. Over the years, I kept looking for any stories in the press about antisound. Quite a few years passed before the technology reached the consumer market in the form of noise-cancelling headphones.

What do you know/think about mh17, cloaking technology, and missing freescale employees? I also read somewhere about another cloaking technology of populating radar screens with an array of false objects to obscure the protected asset.